It is typical in the prior art relating to this area of technology for a radio-frequency quadrupole to have a main body formed, fundamentally, from four, elongate electrode structures, or segments, which include elongate vane tips opposing each other in pairs, and disposed symmetrically about the long axis of the quadrupole. These tips function to concentrate, accelerate and focus a beam of particles in a stream along that axis.
Prior to the advent of the present invention, such segments, normally four in number (as mentioned), which are assembled in the final quadrupole unit to form an appropriate confronting vane-tip configuration with surrounding wall structure, have included, typically, two different kinds of segments, configured with two, quite different cross-sectional configurations. Good illustrations of this situation are found in the disclosures of U.S. Pat. Nos. 4,885,470 (Integrally Formed Radio Frequency Quadrupole) and 4,949,047 (Segmented RFQ Accelerator). Given this kind of construction, it is obvious that the manufacturing process must deal with proper, differentiated forming and machining of two differently shaped segments, and any inventory of segments maintained in a preassembly state must necessarily include both kinds of required segments.
As part of the ever-present need, and commercial desire, to increase simplicity, and to reduce manufacturing and assembling costs, designers in this field have sought ways to deal with the necessary cross-sectional configurations of the usually required four segments, in the hope of addressing these issues. In this setting, the structure proposed by the present invention offers an extraordinary step forward, by providing, and demonstrating, that each of the four segments typically required to build a radio-frequency quadrupole can have a cross section which is identical to that of each other segment. This advance in the art clearly makes an important stride toward improved simplicity, and in addition, greatly minimizes costs relating to manufacture and maintenance of inventory. As an important example of the greatly improved manufacturability of a segment formed in accordance with this invention, what might be thought of as raw segment material can, foundationally, be formed through a process of extrusion, with extruded product then cut into whatever lengths are chosen by a designer. Any final machining operations thereafter, with the exception of certain specific differences required in vane tip configurations, are then exactly the same for each of the four segments required to put together a quadrupole.
Significantly, extruding allows for the precise creation and placement of longitudinally extending coolant-carrying boreholes--boreholes which, in prior art approaches, have had to be drilled, with all of the attendant problems of drill-bit "wanderlust"--the tendency, typically, of a drill bit to drift off axis beyond about 24-inches of drilling depth.
As will become apparent from the drawing illustrations herein, and from the description of the invention which follows, the novel segment structure of this invention springs from a unique asymmetry which exists in segment cross section, which asymmetry ultimately allows four segment units to be joined in such a fashion that the finally assembled unit contains the appropriate degree of bilateral symmetry required in a quadrupole assembly.
Various other objects and advantages which are attained by the invention will become more readily apparent as the mentioned description of the invention which now follows is read in conjunction with the two drawing figures that form part of this disclosure.